1. Field of the Invention
The present invention relates to a thermal transfer printer.
2. Description of the Prior Art
A thermal transfer printer incorporates a head urging apparatus for urging a printing head against a platen in a printing step and for releasing urging of the printing head against the platen in a returning step wherein the printing head is returned to a printing start position.
Known examples of a head urging apparatus of this type are an apparatus including an urging spring for biasing a head holding member in a direction of urging a printing head against a platen and a solenoid for attracting the head holding member in a direction along which the printing head moves away from the platen, and an apparatus using a cam which is rotated in a forward/reverse direction by a stepping motor, an urging spring for biasing a printing head in an urging direction, and a release spring for biasing the printing head in an urging release direction, thereby switching between urging and urging release. However, in either of the head urging apparatuses, an urging force of the printing head against the platen is fixed.
Recently, in order to satisfy various needs of users, demands have arisen for printing on copying machine (PPC) recording paper or so-called rough paper having a rough surface, color printing, high-speed printing, printing using a so-called multi-strike ribbon which can be used a plurality of times, printing on thermal paper for a teleprinter, and the like.
In order to perform good printing on rough paper having a rough surface, an ink ribbon suitable for the paper must be used and an urging force of a printing head against a platen must be set larger. However, if printing is performed on smooth paper under such conditions, transverse lines and scumming are generated. In color printing and high-speed printing, a soft ink ribbon is used. Therefore, if the urging force is kept strong, scumming is generated. In addition, when a multi-strike ribbon is printed with a strong urging force, traces of preceding printing are printed, i.e., a so-called ghost phenomenon occurs. Furthermore, if printing is performed on thermal paper with a strong urging force, tailings, feathering, and transverse lines are generated.
Japanese Patent Laid-Open No. 53-70447 discloses an apparatus in which an urging force of a printing head can be variably set in accordance with the type of thermal paper by operating a manual lever. However, when such an apparatus is used, a user must check the quality of thermal paper and set a head urging force in accordance with a check result, resulting in a troublesome operation for a user. In addition, it is difficult for a user who does not get used to a printer operation to check the quality of thermal paper. For this reason, a head urging force may be wrongly set to pose the same problems as in the fixed-urging force type apparatus.